This invention relates to the fiberization of attenuable materials and is adapted for use in the formation of fibers from various thermoplastic mineral materials, such as glass and similar compositions which are rendered molten by heating. Since the technique of the invention is especially useful in the attenuation of glass and similar thermoplastic materials, the following description refers to the use of glass by way of illustration.
In the attenuation of molten glass in order to effect fiberization by various techniques employing gaseous attenuating blasts or jets, it is ordinarily desirable to arrange the attenuation components and the means for introducing the molten glass in a manner avoiding substantial fragmentation of the glass, the avoidance of such fragmentation being desirable in order to provide for the production of fibers of good length. In addition, in techniques of this type, it is also desirable to provide for fiber production with a minimum expenditure of heat or energy. The technique of the present invention is adapted to achieve these general purposes; and at the same time, to accomplish certain other objectives, as will be explained more fully as this description proceeds.
In prior Application of the present Applicants, Ser. No. 834,541, filed Sept. 19, 1977, there is disclosed an attenuating jet arrangement employing a pair of gaseous jets of substantially equal kinetic energy per unit of volume and whose axes are disposed in substantially the same plane, the two jets inducing ambient gas and converging in a zone so as to provoke mutual impact and lateral spreading of the combined jet flow, the technique of said prior application further providing for the employment of a multiplicity of pairs of such jets arranged in side-by-side relation and sufficiently close to each other so that the lateral spreading of the combined flow of the pairs of jets causes impingement of the combined flow of the pairs upon each other. In this configuration of gaseous jets, the impingement of the pairs of spreading jets upon each other results in the development of pairs of counter-rotating tornadoes, with an intervening zone of laminar flow therebetween. The tornadoes merge downstream of the zone of laminar flow and a stream of molten glass is delivered into each zone of laminar flow from a point offset toward one side of both jets of the pair. This stream is carried by the laminar flow into the influence of the merging flow of the tornadoes. This system provides for introduction of the streams of attenuable material without fragmentation and results in attenuation of relatively long fibers.
In said prior application, the jet system just described is also disclosed in association with a larger gaseous blast, and the combined jet flow of each pair of jets is directed transversely toward the blast and has a higher kinetic energy per unit of volume than the blast, so that each combined jet flow penetrates the blast, thereby developing a zone of interaction in the blast by means of which the fiber being formed is subjected to a second stage of attenuation.
In our prior Applications Ser. No. 873,734, filed Jan. 30, 1978 and No. 829,515, filed Aug. 31, 1977, a jet and blast system of the kind just referred to is also disclosed together with provision for introducing fuel and comburent components into the zones of interaction of the jets in the blast in a manner providing for development of a combustible mixture in said zones of interaction and further providing for ignition of the combustible mixture in said zones of interaction. This provides for localized combustion and elevation of temperature in the attenuation zones within the blast.
In the technique provided according to the present invention, provision is made for the development of a plurality of pairs of side-by-side gaseous jets with the axes of the jets of each pair disposed in substantially the same plane and with the jets converging to a zone of impact and lateral spreading, so that the combined flow of the pairs of jets impinge upon each other and develop the pairs of tornadoes as above described, with an intervening zone of laminar flow; and in addition, in accordance with the technique of the present application, the jets comprise fuel and comburent components in proportions providing a combustible mixture in the combined flow of each pair of jets. Moreover, in accordance with the technique of the present application, conditions are maintained in order to provide for ignition of the combustible mixture in the combined jet flow of each pair of jets, so that a localized elevated attenuating temperature is provided in the jet flow itself, thereby providing for effective attenuation of long fibers without employment of a blast into which the jets are delivered, as in the prior technique referred to above.
The "energy localization" provided by the present invention in the manner just referred to thus provides for energy conservation within the jet system itself, thereby simplifying the equipment since it is not necessary to provide a means for generating a larger blast, as in the prior technique above described.
The technique of the present invention also is particularly advantageous for the attenuation of very hard glass which requires relatively high temperature in order to obtain appropriate viscosity for fiberization. Such relatively high fiberization temperature can readily be attained within the jet flow itself, in view of which the glass supply equipment, such as a bushing, may be maintained at lower temperature than would be required with other fiberization techniques. This, in turn, is of advantage because with hard glasses requiring high temperatures for effective fiberization, such high temperatures detrimentally affect the glass supply bushing or equivalent glass supply means.